U.S. patent application number 15/765007 was filed with the patent office on 2018-10-04 for composition for adhesive layer of non-aqueous secondary battery, adhesive layer for non-aqueous secondary battery, adhesive layer-equipped separator for non-aqueous secondary battery, adhesive layer-equipped electrode for non-aqueous secondary battery, non-aqueous secondary battery, and method for p.
This patent application is currently assigned to ZEON CORPORATION. The applicant listed for this patent is ZEON CORPORATION. Invention is credited to Junnosuke AKIIKE, Yutaka MARUHASHI.
Application Number | 20180287189 15/765007 |
Document ID | / |
Family ID | 58630020 |
Filed Date | 2018-10-04 |
United States Patent
Application |
20180287189 |
Kind Code |
A1 |
MARUHASHI; Yutaka ; et
al. |
October 4, 2018 |
COMPOSITION FOR ADHESIVE LAYER OF NON-AQUEOUS SECONDARY BATTERY,
ADHESIVE LAYER FOR NON-AQUEOUS SECONDARY BATTERY, ADHESIVE
LAYER-EQUIPPED SEPARATOR FOR NON-AQUEOUS SECONDARY BATTERY,
ADHESIVE LAYER-EQUIPPED ELECTRODE FOR NON-AQUEOUS SECONDARY
BATTERY, NON-AQUEOUS SECONDARY BATTERY, AND METHOD FOR PRODUCING
SAME
Abstract
Provided is a composition for an adhesive layer of a non-aqueous
secondary battery allowing formation of an adhesive layer that can
achieve both high process adhesiveness and high blocking resistance
in battery members such as an electrode and a separator. The
presently disclosed composition for an adhesive layer of a
non-aqueous secondary battery includes a particulate polymer A that
has a glass-transition temperature of no higher than 20.degree. C.
and a volume-average particle diameter of at least 100 nm and less
than 450 nm, and a particulate polymer B that has a
glass-transition temperature of at least 30.degree. C. and less
than 60.degree. C. and a volume-average particle diameter larger
than the volume-average particle diameter of the particulate
polymer A.
Inventors: |
MARUHASHI; Yutaka;
(Chiyoda-ku, Tokyo, JP) ; AKIIKE; Junnosuke;
(Chiyoda-ku, Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ZEON CORPORATION |
Chiyoda-ku, Tokyo |
|
JP |
|
|
Assignee: |
ZEON CORPORATION
Chiyoda-ku, Tokyo
JP
|
Family ID: |
58630020 |
Appl. No.: |
15/765007 |
Filed: |
October 7, 2016 |
PCT Filed: |
October 7, 2016 |
PCT NO: |
PCT/JP2016/004529 |
371 Date: |
March 30, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 4/133 20130101;
H01M 10/058 20130101; C09J 2433/003 20130101; C08L 2205/025
20130101; H01M 4/587 20130101; C08L 33/10 20130101; C09J 133/26
20130101; C09J 133/10 20130101; Y02E 60/10 20130101; H01M 4/525
20130101; H01M 2300/0097 20130101; H01M 4/131 20130101; H01M 4/1393
20130101; H01M 10/0565 20130101; H01M 2/1653 20130101; H01M 10/0525
20130101; H01M 2/1686 20130101; H01M 4/1391 20130101; C09J 133/26
20130101; C08L 33/12 20130101 |
International
Class: |
H01M 10/058 20060101
H01M010/058; C08L 33/10 20060101 C08L033/10; C09J 133/10 20060101
C09J133/10 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 28, 2015 |
JP |
2015-211861 |
Claims
1. A composition for an adhesive layer of a non-aqueous secondary
battery, the composition comprising: a particulate polymer A and a
particulate polymer B, wherein the particulate polymer A has a
glass-transition temperature of no higher than 20.degree. C. and a
volume-average particle diameter of at least 100 nm and less than
450 nm, and the particulate polymer B has a glass-transition
temperature of at least 30.degree. C. and less than 60.degree. C.
and a volume-average particle diameter larger than the
volume-average particle diameter of the particulate polymer A.
2. The composition for an adhesive layer of a non-aqueous secondary
battery of claim 1, wherein a content of the particulate polymer A
is at least 20 parts by mass and no greater than 70 parts by mass
per 100 parts by mass of the particulate polymer B.
3. The composition for an adhesive layer of a non-aqueous secondary
battery of claim 1, wherein a degree of swelling in electrolysis
solution of the particulate polymer A is at least a factor of 1 and
no greater than a factor of 10.
4. The composition for an adhesive layer of a non-aqueous secondary
battery of claim 1, wherein a degree of swelling in electrolysis
solution of the particulate polymer B is at least a factor of
6.
5. The composition for an adhesive layer of a non-aqueous secondary
battery of claim 1, wherein the volume-average particle diameter of
the particulate polymer B is at least 200 nm and no greater than
900 nm.
6. An adhesive layer for a non-aqueous secondary battery, the
adhesive layer being formed by using the composition for an
adhesive layer of a non-aqueous secondary battery of claim 1.
7. An adhesive layer-equipped separator for a non-aqueous secondary
battery, the adhesive layer-equipped separator comprising a
separator and the adhesive layer for a non-aqueous secondary
battery of claim 6 provided on at least one surface of the
separator.
8. An adhesive layer-equipped electrode for a non-aqueous secondary
battery, the adhesive layer-equipped electrode comprising an
electrode and the adhesive layer for a non-aqueous secondary
battery of claim 6 provided on at least one surface of the
electrode.
9. A non-aqueous secondary battery comprising: a positive
electrode, a negative electrode, a separator, and the adhesive
layer for a non-aqueous secondary battery of claim 6, wherein the
adhesive layer for a non-aqueous secondary battery is arranged
between the positive electrode and the separator and/or between the
negative electrode and the separator.
10. A method for producing a non-aqueous secondary battery, the
method comprising forming an adhesive layer for a non-aqueous
secondary battery on at least one of a positive electrode, a
negative electrode, and a separator using the composition for an
adhesive layer of a non-aqueous secondary battery of claim 1.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to a composition for an
adhesive layer of a non-aqueous secondary battery, an adhesive
layer for a non-aqueous secondary battery, an adhesive
layer-equipped separator for a non-aqueous secondary battery, an
adhesive layer-equipped electrode for a non-aqueous secondary
battery, a non-aqueous secondary battery, and a method for
producing a non-aqueous secondary battery.
BACKGROUND
[0002] Non-aqueous secondary batteries (also simply referred to
below as "secondary batteries") such as lithium ion secondary
batteries are small and light, high in energy density, and capable
of repeated charging and discharging. Such secondary batteries are
therefore used in a wide variety of applications. In recent years,
improvements in battery members have been studied to obtain even
better performance of non-aqueous secondary batteries.
[0003] A secondary battery such as a lithium ion secondary battery
generally includes battery members such as electrodes (a positive
electrode and a negative electrode) and a separator that isolates
the positive and negative electrodes from each another to prevent
the electrodes from short-circuiting. An adhesive layer or the like
for improving the adhesiveness between battery members may be
provided on the surface of the electrodes and/or the separator.
Specifically, an adhesive layer-equipped electrode obtained by
further forming an adhesive layer on an electrode and an adhesive
layer-equipped separator obtained by forming an adhesive layer on a
separator are used as battery members.
[0004] In the production process of a secondary battery, a battery
member produced to be long is typically wound as produced and then
stored and transported. However, if a battery member including an
adhesive layer, such as an adhesive layer-equipped electrode or an
adhesive layer-equipped separator, is stored and transported in a
wound state, adjacent battery members may adhere via the adhesive
layer. That is, defects and a reduction in productivity may occur
due to blocking. Accordingly, a battery member that includes an
adhesive layer is required to have the capability of inhibiting
blocking during the production process (blocking resistance).
[0005] Patent literature (PTL) 1, for example, proposes an adhesive
for a lithium ion secondary battery, the adhesive including a
particulate polymer that has a glass-transition temperature of at
least -60.degree. C. and no higher than 20.degree. C. and a
particle diameter D50 of at least 300 nm and not greater than 700
nm, and another particulate polymer that has a glass-transition
temperature of at least 60.degree. C. and no higher than
150.degree. C., a predetermined particle diameter, and a
predetermined degree of swelling in electrolysis solution. Forming
an adhesive layer using the adhesive that includes the
aforementioned particulate polymer with a high glass-transition
temperature and the aforementioned particulate polymer with a low
glass-transition temperature as in PTL 1 improves the blocking
resistance of the battery member that includes the formed adhesive
layer while also improving the adhesiveness between battery members
after immersion in an electrolysis solution.
CITATION LIST
Patent Literature
[0006] PTL 1: JP 2015-41603 A
SUMMARY
Technical Problem
[0007] In the production process of a secondary battery, battery
members may be stacked before immersion in an electrolysis solution
and cut to a desired size as necessary and may be transported as a
laminate. During such cutting or transportation, stacked battery
members may become misaligned, leading to problems such as defects
and a reduction in productivity. In addition to the above-described
blocking resistance, battery members are therefore required also to
have high adhesiveness (process adhesiveness) between battery
members during the battery production process. The need for such
process adhesiveness has particularly increased in recent years as
batteries have become larger.
[0008] The battery member including an adhesive layer formed using
the adhesive for a lithium ion secondary battery disclosed in PTL
1, however, has room for improvement in achieving both process
adhesiveness between battery members and a high level of blocking
resistance during the battery production process (i.e. before
immersion in an electrolysis solution).
[0009] Accordingly, one objective of the present disclosure is to
provide a composition for an adhesive layer of a non-aqueous
secondary battery allowing formation of an adhesive layer that can
achieve both high process adhesiveness and high blocking resistance
in battery members such as an electrode and a separator.
[0010] Another objective of the present disclosure is to provide an
adhesive layer for a non-aqueous secondary battery that can achieve
both high process adhesiveness and high blocking resistance in
battery members such as an electrode and a separator.
[0011] Still another objective of the present disclosure is to
provide an adhesive layer-equipped separator for a non-aqueous
secondary battery, and an adhesive layer-equipped electrode for a
non-aqueous secondary battery, that have both high process
adhesiveness and high blocking resistance.
[0012] Still another objective of the present disclosure is to
provide a non-aqueous secondary battery with excellent cell
characteristics, such as output characteristics (in particular,
low-temperature output characteristics).
[0013] Still another objective of the present disclosure is to
provide a method for producing a non-aqueous secondary battery that
allows production of a non-aqueous secondary battery with excellent
cell characteristics, such as output characteristics, while
improving the process adhesiveness and blocking resistance of the
battery members.
Solution to Problem
[0014] We conducted diligent investigation with the aim of solving
the problems described above. We focused on using a composition for
an adhesive layer of a non-aqueous secondary battery containing two
types of particulate polymers with different predetermined
glass-transition temperatures and volume-average particle
diameters. We discovered that using this composition for an
adhesive layer allows formation of an adhesive layer that can
achieve good process adhesiveness and blocking resistance in an
electrode, a separator, and the like during the battery production
process. We also discovered that using this composition for an
adhesive layer allows production of a non-aqueous secondary battery
with excellent cell characteristics, such as output
characteristics, while improving the process adhesiveness and
blocking resistance of battery members, thereby completing the
present disclosure.
[0015] Specifically, the present disclosure aims to advantageously
solve the problems described above by disclosing a composition for
an adhesive layer of a non-aqueous secondary battery that comprises
a particulate polymer A and a particulate polymer B, wherein the
particulate polymer A has a glass-transition temperature of no
higher than 20.degree. C. and a volume-average particle diameter of
at least 100 nm and less than 450 nm, and the particulate polymer B
has a glass-transition temperature of at least 30.degree. C. and
less than 60.degree. C. and a volume-average particle diameter
larger than the volume-average particle diameter of the particulate
polymer A. By such inclusion of two types of particulate polymers
that have predetermined glass-transition temperatures and
volume-average particle diameters, a battery member that includes
an adhesive layer formed using this composition for an adhesive
layer of a non-aqueous secondary battery can be provided with both
high process adhesiveness and high blocking resistance.
[0016] In the present disclosure, the "glass-transition
temperature" can be calculated from a differential scanning
calorimetry (DSC) curve obtained using a differential scanning
calorimeter (reference material: aluminum).
[0017] Furthermore, in the present disclosure, the "volume-average
particle diameter" refers to the particle diameter at which, in a
(volume-based) particle diameter distribution measured by a laser
diffraction method, the cumulative volume calculated from the small
diameter end reaches 50% (D50).
[0018] In the presently disclosed composition for an adhesive layer
of a non-aqueous secondary battery, the content of the particulate
polymer A is preferably at least 20 parts by mass and no greater
than 70 parts by mass per 100 parts by mass of the particulate
polymer B. By the content of the particulate polymer A being set
within the aforementioned range, the blocking resistance and
process adhesiveness of a battery member including an adhesive
layer formed using the composition for an adhesive layer of a
non-aqueous secondary battery can be further improved.
[0019] The degree of swelling in electrolysis solution of the
particulate polymer A is preferably at least a factor of 1 and no
greater than a factor of 10. By the degree of swelling in
electrolysis solution of the particulate polymer A being set within
the aforementioned range, a rise in the internal resistance can be
inhibited and output characteristics can be improved in a
non-aqueous secondary battery provided with the adhesive layer
formed using the composition for an adhesive layer of a non-aqueous
secondary battery.
[0020] In the present disclosure, the "degree of swelling in
electrolysis solution" can be measured using the measurement method
described in the Examples section.
[0021] The degree of swelling in electrolysis solution of the
particulate polymer B is preferably at least a factor of 6. By the
degree of swelling in electrolysis solution of the particulate
polymer B being set to at least a factor of 6, a rise in the
internal resistance can be inhibited and output characteristics can
be further improved in a non-aqueous secondary battery provided
with the adhesive layer formed using the composition for an
adhesive layer of a non-aqueous secondary battery.
[0022] The volume-average particle diameter of the particulate
polymer B is preferably at least 200 nm and no greater than 900 nm.
By the volume-average particle diameter of the particulate polymer
B being set within the aforementioned range, the blocking
resistance of a battery member including an adhesive layer formed
using the composition for an adhesive layer of a non-aqueous
secondary battery can be further improved.
[0023] The present disclosure also aims to advantageously solve the
problems described above by disclosing an adhesive layer for a
non-aqueous secondary battery, the adhesive layer being formed by
using any one of the above-described compositions for a non-aqueous
secondary battery adhesive layer. Through use of such a composition
for an adhesive layer that includes two types of particulate
polymers that have predetermined glass-transition temperatures and
volume-average particle diameters, an adhesive layer that can
achieve both high process adhesiveness and high blocking resistance
in a battery member can be obtained.
[0024] The present disclosure also aims to advantageously solve the
problems described above by disclosing an adhesive layer-equipped
separator for a non-aqueous secondary battery, the adhesive
layer-equipped separator comprising a separator and the
above-described adhesive layer for a non-aqueous secondary battery
provided on at least one surface of the separator. By the presently
disclosed adhesive layer for a non-aqueous secondary battery thus
being provided on at least one surface of the separator, the
blocking resistance of the separator can be improved, while
improving the process adhesiveness between the electrode and the
separator during the battery production process.
[0025] The present disclosure also aims to advantageously solve the
problems described above by disclosing an adhesive layer-equipped
electrode for a non-aqueous secondary battery, the adhesive
layer-equipped electrode comprising an electrode and the
above-described adhesive layer for a non-aqueous secondary battery
provided on at least one surface of the electrode. By the presently
disclosed adhesive layer for a non-aqueous secondary battery thus
being provided on at least one surface of the electrode, the
blocking resistance of the electrode can be improved, while
improving the process adhesiveness between the electrode and the
separator during the battery production process.
[0026] The present disclosure also aims to advantageously solve the
problems described above by disclosing a non-aqueous secondary
battery comprising a positive electrode, a negative electrode, a
separator, and the above-described presently disclosed adhesive
layer for a non-aqueous secondary battery, wherein the adhesive
layer for a non-aqueous secondary battery is arranged between the
positive electrode and the separator and/or between the negative
electrode and the separator. By the above-described adhesive layer
for a non-aqueous secondary battery thus being arranged between the
positive electrode and the separator and/or between the negative
electrode and the separator, the internal resistance of the
secondary battery that is produced can be lowered, and the cell
characteristics, such as output characteristics, can be
sufficiently improved.
[0027] The present disclosure also aims to advantageously solve the
problems described above by disclosing a method for producing a
non-aqueous secondary battery, the method comprising forming an
adhesive layer for a non-aqueous secondary battery on at least one
of a positive electrode, a negative electrode, and a separator
using the above-described presently disclosed composition for an
adhesive layer of a non-aqueous secondary battery. By such
inclusion of a step of forming a predetermined adhesive layer at a
predetermined position, a non-aqueous secondary battery with
excellent cell characteristics, such as output characteristics, can
be produced while improving the process adhesiveness and blocking
resistance of the battery members.
Advantageous Effect
[0028] The present disclosure can provide an adhesive layer for a
non-aqueous secondary battery that can achieve both high process
adhesiveness and high blocking resistance in battery members such
as an electrode and a separator and can provide a composition for
an adhesive layer of a non-aqueous secondary battery capable of
forming this adhesive layer.
[0029] The present disclosure can also provide an adhesive
layer-equipped separator for a non-aqueous secondary battery, and
an adhesive layer-equipped electrode for a non-aqueous secondary
battery, that have both high process adhesiveness and high blocking
resistance.
[0030] The present disclosure can also provide a non-aqueous
secondary battery with excellent cell characteristics, such as
output characteristics, and a method for producing a non-aqueous
secondary battery that allows production of the non-aqueous
secondary battery while improving the process adhesiveness and
blocking resistance of the battery members.
DETAILED DESCRIPTION
[0031] Embodiments of the present disclosure will now be
described.
[0032] The presently disclosed composition for an adhesive layer of
a non-aqueous secondary battery can be used when forming an
adhesive layer for a non-aqueous secondary battery. The adhesive
layer formed using the composition for an adhesive layer of a
non-aqueous secondary battery can be used when adhering a separator
and an electrode. The adhesive layer-equipped separator for a
non-aqueous secondary battery or adhesive layer-equipped electrode
for a non-aqueous secondary battery obtained by using the
composition for an adhesive layer of a non-aqueous secondary
battery to form an adhesive layer for a non-aqueous secondary
battery on a separator or an electrode can be suitably used when
producing a non-aqueous secondary battery such as a lithium ion
secondary battery. The presently disclosed non-aqueous secondary
battery includes the presently disclosed adhesive layer for a
non-aqueous secondary battery between the positive electrode and
the separator and/or between the negative electrode and the
separator. The presently disclosed non-aqueous secondary battery
can, for example, be produced using the presently disclosed method
for producing a non-aqueous secondary battery.
[0033] The presently disclosed composition for an adhesive layer of
a non-aqueous secondary battery and adhesive layer for a
non-aqueous secondary battery can be suitably used in particular
when producing an adhesive layer-equipped separator for a
non-aqueous secondary battery. The member on which the adhesive
layer is formed, such as the electrode, the separator, or the like,
is also referred to below simply as a "substrate".
[0034] (Composition for Adhesive Layer of Non-Aqueous Secondary
Battery)
[0035] The presently disclosed composition for an adhesive layer of
a non-aqueous secondary battery contains a particulate polymer A
having a predetermined glass-transition temperature and a
predetermined volume-average particle diameter and a particulate
polymer B having a predetermined glass-transition temperature and a
predetermined volume-average particle diameter that differ from
those of the particulate polymer A. The composition for an adhesive
layer of a non-aqueous secondary battery is normally a slurry
composition with water or the like as a dispersion medium and can
include any additives in addition to the aforementioned particulate
polymers and dispersion medium. Because the presently disclosed
composition for an adhesive layer of a non-aqueous secondary
battery includes at least two types of particulate polymers, good
process adhesiveness is obtained between the electrode and the
separator during the battery production process when an adhesive
layer for a non-aqueous secondary battery is provided on the
electrode or the separator using the composition for an adhesive
layer. Good blocking resistance is also obtained for the electrode
provided with the adhesive layer and the separator provided with
the adhesive layer.
[0036] <Particulate Polymer A>
[0037] When an adhesive layer is provided on the substrate, such as
the separator or electrode, using the composition for an adhesive
layer of a non-aqueous secondary battery that includes the
particulate polymer A, the particulate polymer A has the function
of allowing the particulate polymer A itself and the particulate
polymer B used in combination to adhere well to the substrate. In
other words, the particulate polymer A allows the adhesive layer
for a non-aqueous secondary battery formed on the substrate to
achieve good adhesiveness with the substrate. Furthermore, via the
adhesive layer for a non-aqueous secondary battery containing the
particulate polymer A, the particulate polymer A also has the
function of adhering the electrode and the separator with good
process adhesiveness and of preventing misalignment of the
separator or the like during the battery production process.
[0038] <<Properties>>
[Glass-Transition Temperature]
[0039] Here, the glass-transition temperature of the particulate
polymer A needs to be no higher than 20.degree. C. The
glass-transition temperature of the particulate polymer A is
preferably no higher than 10.degree. C., more preferably no higher
than 5.degree. C., even more preferably no higher than -10.degree.
C., and still more preferably no higher than -20.degree. C., and is
preferably at least -60.degree. C., more preferably at least
-50.degree. C., and even more preferably at least -40.degree. C. By
inclusion of the particulate polymer A with a glass-transition
temperature of no higher than 20.degree. C. in the composition for
an adhesive layer, a battery member including an adhesive layer
formed using the composition for an adhesive layer can be provided
with high process adhesiveness, and dusting of the adhesive layer
formed by good adhesion between the substrate and the adhesive
layer can be inhibited. Furthermore, if the glass-transition
temperature of the particulate polymer A is at least -60.degree.
C., the particulate polymer A can be prepared easily, and a battery
member including the adhesive layer achieves good blocking
resistance.
[0040] [Volume-Average Particle Diameter]
[0041] The volume-average particle diameter of the particulate
polymer A needs to be at least 100 nm and less than 450 nm. The
volume-average particle diameter of the particulate polymer A is
preferably at least 200 nm and more preferably at least 300 nm and
is preferably no greater than 400 nm and more preferably less than
400 nm. If the volume-average particle diameter of the particulate
polymer A is at least 100 nm, the stability of the slurry
composition constituting the composition for an adhesive layer can
be improved. Specifically, when stirring the composition for an
adhesive layer with a high shear force and when coating at high
speed, the occurrence of aggregations in the composition for an
adhesive layer can be inhibited. Furthermore, if the volume-average
particle diameter of the particulate polymer A is less than 450 nm
and moreover is smaller than the volume-average particle diameter
of the particulate polymer B, the blocking resistance of the
battery member including the formed adhesive layer can be
improved.
[0042] The volume-average particle diameter of the particulate
polymer A can be adjusted to within a desired range by, for
example, the type of particulate polymers, the polymerization
method, the polymerization conditions, or by separating or
classifying precipitates of the obtained polymer.
[0043] [Degree of Swelling in Electrolysis Solution]
[0044] The degree of swelling in electrolysis solution of the
particulate polymer A is preferably at least a factor of 1, more
preferably at least a factor of 2, and even more preferably at
least a factor of 3, and is preferably at most a factor of 10, more
preferably at most a factor of 8, even more preferably at most a
factor of 6, and still more preferably at most a factor of 5. If
the degree of swelling in electrolysis solution of the particulate
polymer A is at least a factor of 1, the ion conductivity increases
and a rise in internal resistance can be inhibited in a secondary
battery provided with the adhesive layer containing the particulate
polymer A. Consequently, the produced secondary battery can be
provided with excellent output characteristics. Furthermore, if the
degree of swelling in electrolysis solution of the particulate
polymer A is no greater than a factor of 10, the particulate
polymer A included in the adhesive layer can be prevented from
swelling excessively in electrolysis solution and reducing the gaps
in the adhesive layer (which are filled by the swollen particulate
polymer A), and a reduction in the ion conductivity of the adhesive
layer can be inhibited. As a result, a rise in the resistance of
the produced secondary battery is inhibited, yielding good output
characteristics.
[0045] <<Content>>
[0046] The content of the particulate polymer A in the composition
for an adhesive layer of a non-aqueous secondary battery per 100
parts by mass of the particulate polymer B is preferably at least
20 parts by mass, more preferably at least 25 parts by mass, even
more preferably at least 30 parts by mass, and still more
preferably at least 40, and is preferably no greater than 70 parts
by mass, more preferably no greater than 65 parts by mass, and even
more preferably no greater than 60 parts by mass. If the content of
the particulate polymer A is at least the aforementioned lower
limit, the substrate and the adhesive layer formed on the substrate
adhere well because of the contribution of the particulate polymer
A. Additionally, the process adhesiveness of the battery members
(adhesive layer-equipped electrode, adhesive layer-equipped
separator) obtained by forming an adhesive layer on a substrate can
be further improved. Furthermore, if the content of the particulate
polymer A is no greater than the aforementioned upper limit, a rise
in internal resistance is inhibited by inhibiting the reduction in
gaps in the adhesive layer, and because of the contribution of the
particulate polymer B used in combination, the blocking resistance
of the battery members that include the adhesive layer can be
further improved.
[0047] <<Composition>>
[0048] The polymer constituting the particulate polymer A is not
specifically limited so long as the polymer has the above-described
glass-transition temperature and volume-average particle diameter,
and any polymer such as an acrylic-based polymer, a conjugated
diene-based polymer, or an unsaturated carboxylic acid-based
polymer can be used.
[0049] Here, a conjugated diene-based polymer refers to a polymer
containing a conjugated diene monomer unit. Examples of the
conjugated diene-based polymer are not specifically limited and
include a copolymer including an aromatic vinyl monomer unit and an
aliphatic conjugated diene monomer unit, such as a
styrene-butadiene copolymer (SBR); butadiene rubber (BR); acrylic
rubber (NBR) (a copolymer including an acrylonitrile unit and a
butadiene unit); hydrides thereof; and the like.
[0050] The acrylic-based polymer is a polymer that includes a
(meth)acrylic acid ester monomer unit. Here, a (meth)acrylic acid
alkyl ester such as methyl acrylate, ethyl acrylate, butyl
acrylate, methyl methacrylate, ethyl methacrylate, 2-ethylhexyl
acrylate, or the like can be used as the (meth)acrylic acid ester
monomer that can form a (meth)acrylic acid ester monomer unit.
[0051] In the present disclosure, "(meth)acryl" is used to indicate
"acryl" and/or "methacryl".
[0052] The unsaturated carboxylic acid-based polymer is a polymer
that includes an unsaturated carboxylic acid monomer unit. Here,
acrylic acid, methacrylic acid, itaconic acid, and the like can be
used as the unsaturated carboxylic acid that can form an
unsaturated carboxylic acid monomer unit.
[0053] <<Method for Preparing Particulate Polymer
A>>
[0054] No specific limitations are placed on the mode of
polymerization of the particulate polymer A. For example, any
method among solution polymerization, suspension polymerization,
bulk polymerization, and emulsion polymerization may be used. As
the polymerization reaction, addition polymerization such as ionic
polymerization, radical polymerization, or living radical
polymerization can be used. The polymerization may be carried out
with a commonly used emulsifier, dispersant, polymerization
initiator, chain transfer agent, or the like that are usable for
polymerization, and the amount thereof may also be the same as
commonly used.
[0055] <Particulate Polymer B>
[0056] The particulate polymer B has the function of allowing
battery members provided with the adhesive layer for a non-aqueous
secondary battery formed using the composition for an adhesive
layer of a non-aqueous secondary battery that contains the
particulate polymer A and the particulate polymer B to achieve high
blocking resistance and process adhesiveness. In other words, when
a battery member provided with the adhesive layer for a non-aqueous
secondary battery that contains the particulate polymer B is wound
as produced and then stored and transported, the particulate
polymer B has the function of inhibiting adhesion between adjacent
battery members via the adhesive layer and also of adhering the
electrode and the separator with good process adhesiveness and of
preventing misalignment of the separator and the like during the
battery production process.
[0057] <<Properties>>
[Glass-Transition Temperature]
[0058] Here, the glass-transition temperature of the particulate
polymer B needs to be at least 30.degree. C. and less than
60.degree. C. In other words, the glass-transition temperature of
the particulate polymer B is higher than the glass-transition
temperature of the above-described particulate polymer A. The
glass-transition temperature of the particulate polymer B is
preferably at least 35.degree. C. and more preferably at least
40.degree. C. and is preferably no higher than 55.degree. C. and
more preferably no higher than 50.degree. C. By inclusion of the
particulate polymer B with a glass-transition temperature of at
least 30.degree. C. in the composition for an adhesive layer, a
battery member including the adhesive layer formed using the
composition for an adhesive layer can be provided with excellent
blocking resistance during storage or transportation of the battery
member. Furthermore, by inclusion of the particulate polymer B with
the glass-transition temperature of less than 60.degree. C. in the
composition for an adhesive layer, a battery member including the
adhesive layer can be provided with high blocking resistance while
also being provided with good process adhesiveness.
[0059] [Volume-Average Particle Diameter]
[0060] The volume-average particle diameter of the particulate
polymer B needs to be larger than the volume-average particle
diameter of the particulate polymer A. For example, the
volume-average particle diameter of the particulate polymer B is
preferably at least 1.1 times larger than the volume-average
particle diameter of the particulate polymer A and is more
preferably at least 1.2 times larger. If the particle diameter of
the particulate polymer B, which has a relatively low adhesive
strength at a normal temperature due to the high glass-transition
temperature, is larger than the particle diameter of the
particulate polymer A, which has a low glass-transition temperature
and achieves high adhesive strength, then the particulate polymer B
functions like a spacer and can inhibit blocking.
[0061] The volume-average particle diameter of the particulate
polymer B is preferably at least 200 nm, more preferably at least
300 nm, even more preferably at least 400 nm, and still more
preferably at least 470 nm, and is preferably no greater than 900
nm, more preferably no greater than 800 nm, even more preferably no
greater than 700 nm, and still more preferably no greater than 600
nm. If the volume-average particle diameter of the particulate
polymer B is at least 200 nm, the blocking resistance of a battery
member provided with the formed adhesive layer can be further
improved. If the volume-average particle diameter of the
particulate polymer B is no greater than 900 nm, precipitation of
solid components (a reduction in the dispersibility of the slurry)
in the composition for an adhesive layer containing the particulate
polymer B can be inhibited.
[0062] The volume-average particle diameter of the particulate
polymer B can be adjusted with a similar method to the one
described above for the particulate polymer A.
[0063] [Degree of Swelling in Electrolysis Solution]
[0064] The degree of swelling in electrolysis solution of the
particulate polymer B is preferably at least a factor of 6, more
preferably at least a factor of 10, and even more preferably at
least a factor of 15. If the degree of swelling in electrolysis
solution of the particulate polymer B is at least a factor of 6,
the ion conductivity increases and a rise in internal resistance
can be inhibited in a secondary battery provided with the adhesive
layer containing the particulate polymer B. Consequently, the
produced secondary battery can be provided with excellent output
characteristics.
[0065] The degree of swelling in electrolysis solution of the
particulate polymer B is not specifically limited, as long as the
particulate polymer B does not dissolve in the electrolysis
solution, but is normally no greater than a factor of 40 and can,
for example, be set to no greater than a factor of 30.
[0066] <<Composition>>
[0067] The polymer constituting the particulate polymer B is not
specifically limited so long as the polymer has the above-described
glass-transition temperature and volume-average particle diameter,
and any polymer like the polymer constituting the above-described
particulate polymer A, for example, can be used.
[0068] <<Method for Preparing Particulate Polymer
B>>
[0069] No specific limitations are placed on the mode of
polymerization of the particulate polymer B. For example, any
method among solution polymerization, suspension polymerization,
bulk polymerization, and emulsion polymerization may be used. As
the polymerization reaction, addition polymerization such as ionic
polymerization, radical polymerization, or living radical
polymerization can be used. The polymerization may be carried out
with a commonly used crosslinkable monomer, emulsifier,
polymerization initiator, dispersant, chain transfer agent, or the
like that are usable for polymerization, and the amount thereof may
also be the same as commonly used.
[0070] <Additives>
[0071] The additives that the presently disclosed composition for
an adhesive layer of a non-aqueous secondary battery may optionally
include are not specifically limited. Examples include components
such as a surface tension modifier, a different dispersant than the
dispersant used in the aforementioned polymerization, a viscosity
modifier, a reinforcing material, and an additive for electrolysis
solution. These components may be commonly known materials such as
those described in WO 2012/115096 A1 and are not specifically
limited other than being materials that do not affect the battery
reaction. One of these components may be used individually, or two
or more of these components may be used in combination in a freely
selected ratio.
[0072] <Method for Preparing Composition for Adhesive Layer of
Non-Aqueous Secondary Battery>
[0073] The presently disclosed composition for an adhesive layer of
a non-aqueous secondary battery is not specifically limited, apart
from containing the above-described particulate polymer A and
particulate polymer B that have predetermined glass-transition
temperatures and volume-average particle diameters, and can be
prepared by stirring and mixing the particulate polymer A, the
particulate polymer B, and the above-described optional additives
in the presence of a dispersion medium. When preparing the
composition for an adhesive layer using a dispersion liquid of
particulate polymers, the liquid component contained in the
dispersion liquid can be used as is as the dispersion medium of the
composition for an adhesive layer.
[0074] Here, the stirring method is not specifically limited, and a
known method may be used. Specifically, the composition for an
adhesive layer can be prepared in slurry form by mixing the
aforementioned components and dispersion medium using a typical
stirring vessel, ball mill, sand mill, bead mill, pigment
disperser, ultrasonic disperser, grinding machine, homogenizer,
planetary mixer, FILMIX, or the like. Mixing of the aforementioned
components and the dispersion medium can normally be performed for
a period of 10 minutes to several hours in a temperature range of
room temperature to 80.degree. C.
[0075] As described above, the particulate polymer A and the
particulate polymer B may be polymerized in the composition for an
adhesive layer of a non-aqueous secondary battery or may exist
separately, but these polymers preferably exist separately. When
the particulate polymer A and the particulate polymer B exist
separately, they may exist separately without coming into contact
at all in the composition for an adhesive layer of a non-aqueous
secondary battery, or they may come into contact locally while
still existing separately as a whole. The particulate polymer A and
the particulate polymer B can achieve their respective functions
(such as process adhesiveness and improvement of blocking
resistance) better by existing separately. For example, in more
detail, the presently disclosed composition for an adhesive layer
of a non-aqueous secondary battery is preferably prepared by
polymerizing the particulate polymer A and the particulate polymer
B individually in different reaction systems and then dispersing
the particulate polymer A and the particulate polymer B in a
dispersion medium with the above-described optional components.
[0076] (Adhesive Layer for Non-Aqueous Secondary Battery)
[0077] The presently disclosed adhesive layer for a non-aqueous
secondary battery is, for example, formed on a separator and/or an
electrode using the composition for an adhesive layer of a
non-aqueous secondary battery. In other words, the presently
disclosed adhesive layer for a non-aqueous secondary battery
contains at least the above-described particulate polymer A and
particulate polymer B. By the formed adhesive layer containing the
above-described particulate polymer A and particulate polymer B,
each battery member including the adhesive layer is provided with
good process adhesiveness. Furthermore, because the formed adhesive
layer includes the above-described particulate polymer B, which has
a larger particle diameter than the particulate polymer A, the
battery member including the adhesive layer is provided with good
blocking resistance.
[0078] To achieve good process adhesiveness, the presently
disclosed adhesive layer for a non-aqueous secondary battery is
preferably formed on a separator. The presently disclosed adhesive
layer for a non-aqueous secondary battery may also be formed on a
releasable substrate and then peeled and stacked on (transferred
to) a separator, an electrode, or the like.
[0079] While the particulate polymer A and the particulate polymer
B exist in the composition for an adhesive layer of a non-aqueous
secondary battery in particulate form, they may exist in
particulate form or in any other form in the formed adhesive layer
for a non-aqueous secondary battery.
[0080] <Method for Forming Adhesive Layer for Non-Aqueous
Secondary Battery>
[0081] Examples of methods for forming an adhesive layer for a
non-aqueous secondary battery on the above-described substrate,
such as a separator, an electrode, or a releasable substrate,
include the following.
1) A method for applying the composition for an adhesive layer of a
non-aqueous secondary battery on the surface of a substrate and
then drying the composition applied on the surface of the
substrate; and 2) A method for immersing a substrate into the
composition for an adhesive layer of a non-aqueous secondary
battery and drying the composition applied to the substrate by
immersion.
[0082] Of these methods, the method described in 1) is particularly
preferable because it allows the thickness of the adhesive layer to
be easily controlled. The method described in 1) more specifically
includes a step of applying the composition for an adhesive layer
onto a separator or an electrode (application step) and a step of
drying the composition for an adhesive layer applied on the
separator or the electrode to form an adhesive layer (drying
step).
[0083] The adhesive layer may be formed only on one surface or on
both surfaces of the separator or electrode in accordance with the
structure of the secondary battery to be produced. For example,
when using a separator as the substrate, the adhesive layer is
preferably formed on both surfaces of the separator, whereas when
using an electrode as the substrate, the adhesive layer is
preferably formed on one surface, in particular on the electrode
mixed material layer.
[0084] <<Application Step>>
[0085] No specific limitations are placed on the method by which
the composition for an adhesive layer is applied onto the substrate
in the application step. Examples of the method include spray
coating, doctor blading, reverse roll coating, direct roll coating,
gravure coating, extrusion coating, and brush coating.
[0086] <<Drying Step>>
[0087] In the drying step, the composition for an adhesive layer on
the substrate may be dried by any commonly known method, without
any specific limitations. Examples of the method include drying by
warm, hot, or low-humidity air; vacuum drying; or drying by
irradiation with infrared light or electron beams. Although no
specific limitations are placed on the drying conditions, the
drying temperature is preferably from 30.degree. C. to 80.degree.
C., and the drying time is preferably from 30 seconds to 10
minutes.
[0088] The thickness of the adhesive layer formed on the substrate
is preferably at least 0.01 .mu.m, more preferably at least 0.1
.mu.m, and even more preferably at least 0.5 .mu.m, and is
preferably no greater than 10 .mu.m, more preferably no greater
than 5 .mu.m, and even more preferably no greater than 1 .mu.m. If
the thickness of the adhesive layer is at least the lower limit of
the aforementioned range, the adhesive layer can be provided with
sufficient strength. If the thickness of the adhesive layer is no
greater than the upper limit of the aforementioned range, the ion
conductivity of the adhesive layer in the battery can be ensured,
and the output characteristics and the like of the secondary
battery provided with the adhesive layer can be further
improved.
[0089] (Adhesive Layer-Equipped Separator for Non-Aqueous Secondary
Battery)
[0090] The presently disclosed adhesive layer-equipped separator
for a non-aqueous secondary battery has the adhesive layer for a
non-aqueous secondary battery formed as described above on a
separator. In other words, the presently disclosed adhesive
layer-equipped separator for a non-aqueous secondary battery
includes an adhesive layer containing the above-described
particulate polymer A and particulate polymer B on at least one
surface of a separator. In the adhesive layer-equipped separator
for a non-aqueous secondary battery, the adhesive layer formed on
one or both surfaces of the separator contains the above-described
particulate polymer A and particulate polymer B and thus adheres
well to the separator. The adhesive layer formed on one or both
surfaces of the separator can adhere the adhesive layer-equipped
separator and an electrode together well during production of a
secondary battery. In other words, the formed adhesive layer allows
the adhesive layer-equipped separator to achieve good process
adhesiveness. Furthermore, because the formed adhesive layer
includes the above-described particulate polymer B, which has a
larger particle diameter than the particulate polymer A, the
adhesive layer-equipped separator has good blocking resistance.
[0091] Here, the separator provided with the adhesive layer is not
specifically limited. Examples of the separator include a separator
constituted by an organic separator substrate and a separator
obtained by forming a porous membrane that includes non-conductive
particles and a binder on an organic separator substrate. The
organic separator substrate is a porous member composed of organic
material and is not specifically limited. For example, the organic
separator substrate disclosed in JP 2012-204303 A may be used. Of
these separators, a fine porous membrane made of polyolefinic
(i.e., polyethylene, polypropylene, polybutene, or polyvinyl
chloride) resin is preferred because such a membrane can reduce the
total thickness of the separator, such as an organic separator
substrate, thereby increasing the ratio of electrode active
material in a secondary battery and consequently increasing the
capacity per volume.
[0092] <Method for Forming Adhesive Layer-Equipped Separator for
Non-Aqueous Secondary Battery>
[0093] The method for forming an adhesive layer-equipped separator
for a non-aqueous secondary battery is not specifically limited.
Examples include a method similar to the above-described method for
forming an adhesive layer for a non-aqueous secondary battery. An
example of a preferred formation method is the above-described
method of 1).
[0094] (Adhesive Layer-Equipped Electrode for Non-Aqueous Secondary
Battery)
[0095] The presently disclosed adhesive layer-equipped electrode
for a non-aqueous secondary battery has the adhesive layer for a
non-aqueous secondary battery formed as described above on an
electrode (positive electrode or negative electrode). In other
words, the presently disclosed adhesive layer-equipped electrode
for a non-aqueous secondary battery includes an adhesive layer
containing the above-described particulate polymer A and
particulate polymer B on at least one surface of an electrode. In
the adhesive layer-equipped electrode for a non-aqueous secondary
battery, the adhesive layer formed on one or both sides of the
electrode contains the above-described particulate polymer A and
particulate polymer B and thus adheres well to the electrode. The
adhesive layer formed on one or both surfaces of the electrode can
adhere the adhesive layer-equipped electrode and a separator
together well during production of a secondary battery. In other
words, the formed adhesive layer allows the adhesive layer-equipped
electrode to achieve good process adhesiveness. Furthermore,
because the formed adhesive layer includes the above-described
particulate polymer B, which has a larger particle diameter than
the particulate polymer A, the adhesive layer-equipped electrode
has good blocking resistance.
[0096] Here, as the electrode including the adhesive layer, an
electrode with an electrode mixed material layer formed on a
current collector is normally used. The electrode may further have
a porous membrane (a reinforcing layer, a heat resistant layer, or
the like) that includes non-conductive particles and a binder on
the electrode mixed material layer.
[0097] The current collector may be made of a metal material such
as iron, copper, aluminum, nickel, stainless steel, titanium,
tantalum, gold, or platinum. Of these metal materials, the current
collector for a negative electrode is preferably made of copper.
The current collector for a positive electrode is preferably made
of aluminum.
[0098] The electrode mixed material layer may be a layer containing
an electrode active material and a binder (binder for electrode
mixed material layer). For example, the electrode mixed material
layer may be, but is not specifically limited to, the electrode
mixed material layer disclosed in JP 2013-145763 A.
[0099] Furthermore, a known method may be used for forming the
electrode mixed material layer on the current collector.
[0100] <Method for Forming Adhesive Layer-Equipped Electrode for
Non-Aqueous Secondary Battery>
[0101] The method for forming an adhesive layer-equipped electrode
for a non-aqueous secondary battery is not specifically limited.
Examples include a method similar to the above-described method for
forming an adhesive layer for a non-aqueous secondary battery. An
example of a preferred formation method is the above-described
method of 1).
[0102] (Non-Aqueous Secondary Battery)
[0103] The presently disclosed non-aqueous secondary battery
includes electrodes (positive electrode, negative electrode), a
separator, and the above-described adhesive layer for a non-aqueous
secondary battery between the positive electrode and the separator
and/or between the negative electrode and the separator. Normally,
the electrodes, separator, and adhesive layer function as a battery
in a state of immersion in electrolysis solution. In other words,
the above-described adhesive layer-equipped electrodes for a
non-aqueous secondary battery and the separator may be arranged
with the adhesive layer for a non-aqueous secondary battery
therebetween, or the above-described adhesive layer-equipped
separator for a non-aqueous secondary battery and the electrodes
may be arranged with the adhesive layer for a non-aqueous secondary
battery therebetween. An independently formed adhesive layer for a
non-aqueous secondary battery may also be provided between the
electrodes and the separator. Among these configurations, arranging
the adhesive layer-equipped separator for a non-aqueous secondary
battery and the electrodes so that the adhesive layer for a
non-aqueous secondary battery is therebetween is preferable for
achieving high adhesiveness and ease of production. Because the
presently disclosed non-aqueous secondary battery includes the
presently disclosed adhesive layer for a non-aqueous secondary
battery between the electrodes and the separator, the secondary
battery can achieve excellent output characteristics (in
particular, low-temperature output characteristics) as a result of
having high ion conductivity and low battery resistance inside the
battery.
[0104] The electrodes that do not have an adhesive layer and the
separator that does not have an adhesive layer are not specifically
limited, and an electrode and separator such as those before
adhesive layer formation in the above sections "adhesive
layer-equipped electrode for non-aqueous secondary battery" and
"adhesive layer-equipped separator for non-aqueous secondary
battery" may be used for each. Known electrolysis solutions used in
non-aqueous secondary batteries can be used as the electrolysis
solution.
[0105] <Electrolysis Solution>
[0106] As the electrolysis solution, an organic electrolysis
solution obtained by dissolving a supporting electrolyte into an
organic solvent is normally used. For example, when the non-aqueous
secondary battery is a lithium ion secondary battery, a lithium
salt is used as the supporting electrolyte. Examples of lithium
salts include LiPF.sub.6, LiAsF.sub.6, LiBF.sub.4, LiSbF.sub.6,
LiAlCl.sub.4, LiClO.sub.4, CF.sub.3SO.sub.3Li,
C.sub.4F.sub.9SO.sub.3Li, CF.sub.3COOLi, (CF.sub.3CO).sub.2NLi,
(CF.sub.3SO.sub.2).sub.2NLi, and (C.sub.2F.sub.5SO.sub.2)NLi. Of
these lithium salts, LiPF.sub.6, LiClO.sub.4, and
CF.sub.3SO.sub.3Li are preferable in that they easily dissolve in
solvent and exhibit a high degree of dissociation, with LiPF.sub.6
being particularly preferable. Electrolytes may be used alone or in
combination at any ratio. Normally, lithium ion conductivity tends
to increase as a supporting electrolyte with a higher degree of
dissociation is used. Therefore, lithium ion conductivity can be
adjusted by the type of supporting electrolyte.
[0107] Any organic solvent that can dissolve the supporting
electrolyte can be used as the organic solvent in the electrolysis
solution. Preferred examples include carbonates such as dimethyl
carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC),
propylene carbonate (PC), butylene carbonate (BC), and ethylmethyl
carbonate (EMC); esters such as .gamma.-butyrolactone and methyl
formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran;
and sulfur-containing compounds such as sulfolane and dimethyl
sulfoxide. A mixed solution of these solvents may also be used. Of
these solvents, carbonates are preferable for their high dielectric
constant and broad stable potential region, and a mixture of
ethylene carbonate and ethylmethyl carbonate is more
preferable.
[0108] Moreover, a known additive such as vinylene carbonate (VC),
fluoroethylene carbonate (FEC), or ethyl methyl sulfone may be
added to the electrolysis solution.
[0109] (Method for Producing Non-Aqueous Secondary Battery)
[0110] The presently disclosed method for producing a non-aqueous
secondary battery includes a step of forming an adhesive layer for
a non-aqueous secondary battery on at least one of an electrode
(positive electrode, negative electrode) and a separator using the
above-described composition for an adhesive layer of a non-aqueous
secondary battery (adhesive layer formation step). The presently
disclosed method for producing a non-aqueous secondary battery may
also include a step of adhering the electrode (positive electrode,
negative electrode) and the separator via the adhesive layer for a
non-aqueous secondary battery (adhesion step) and a step of
assembling the battery. Because the presently disclosed method for
preparing a non-aqueous secondary battery includes the step of
forming the adhesive layer for a non-aqueous secondary battery,
non-aqueous secondary batteries can be produced with good
productivity while providing the battery members with good blocking
resistance and process adhesiveness.
[0111] <Adhesive Layer Formation Step>
[0112] In the adhesive layer formation step, an adhesive layer is
formed on at least one of the positive electrode, the negative
electrode, and the separator using the above-described composition
for an adhesive layer of a non-aqueous secondary battery. This
adhesive layer formation step is not specifically limited and may,
for example, be performed using a similar method to the
above-described method for forming the adhesive layer for a
non-aqueous secondary battery. For ease of coating the composition
for an adhesive layer of a non-aqueous secondary battery, the
adhesive layer is preferably formed on at least the separator.
[0113] <Adhesion Step>
[0114] In the adhesion step, the positive electrode and the
separator and/or the negative electrode and the separator are
adhered via the above-described adhesive layer for a non-aqueous
secondary battery, with the positive electrode and the separator
and also the negative electrode and the separator preferably being
adhered. A laminate having the electrodes, the separator, and an
adhesive layer between the electrodes and the separator is thus
obtained. The adhesion temperature during the adhesion step is not
specifically limited, but using the glass-transition temperature
(Tg.sub.B) of the particulate polymer B as a standard, the adhesion
temperature is preferably at least -20.degree. C., more preferably
at least -10.degree. C., and even more preferably at least
-5.degree. C., and is preferably no higher than +35.degree. C.,
more preferably no higher than +30.degree. C., and even more
preferably no higher than +20.degree. C. By adhering the electrodes
and the separator at a temperature that is at least the Tg.sub.B of
-20.degree. C., the particulate polymer B can achieve better
adhesiveness, and good process adhesiveness can be obtained. By
adhering the electrodes and the separator at a temperature that is
no higher than the Tg.sub.B of +35.degree. C., the adhesion step
can be performed while preventing the gaps in the adhesive layer
from being filled by particulate polymer or the like due to
excessive softening of the particulate polymer B, and good
low-temperature output characteristics can be obtained in the
produced secondary battery.
[0115] The adhesion itself is not specifically limited and may be
carried out by, for example, applying any level of pressure to a
laminate including electrodes, a separator, and an adhesive layer
between the electrodes and the separator. The application of
pressure is not specifically limited and can be performed using a
pressure device such as a role press or a flat plate press. The
pressure may, for example, be from 0.1 MPa to 10 MPa. The adhesion
step may be performed only once or may be performed two or more
times.
[0116] <Assembly Step>
[0117] The presently disclosed method for producing a non-aqueous
secondary battery is not particularly limited apart from inclusion
of the above-described adhesive layer formation step and allows
production of a non-aqueous secondary battery using a known
assembly method. Specifically, the presently disclosed method for
producing a non-aqueous secondary battery allows production of a
non-aqueous secondary battery by stacking electrodes (positive
electrode, negative electrode), a separator, and an adhesive layer
between the positive electrode and the separator and/or between the
negative electrode and the separator into a laminate, winding or
folding the laminate as necessary into a battery shape, placing the
laminate in a battery container, filling the battery container with
an electrolysis solution, and sealing the container. In order to
prevent increased internal pressure of the non-aqueous secondary
battery, the occurrence of overcharging or overdischarging, or the
like, an overcurrent preventing device, such as a fuse or a PTC
device; an expanded metal; or a lead plate may be provided as
necessary. The secondary battery may be of any shape, such as a
coin, button, sheet, cylindrical, square, or flat shape.
EXAMPLES
[0118] Hereinafter, the present disclosure will be specifically
described with reference to Examples; however, the disclosure is
not limited to the Examples. In the following, "%" and "parts" used
in expressing quantities are by mass, unless otherwise
specified.
[0119] In the Examples and the Comparative Examples, the
glass-transition temperature, volume-average particle diameter, and
degree of swelling in electrolysis solution of the particulate
polymers; the blocking resistance of an adhesive layer-equipped
separator or an adhesive layer-equipped positive electrode; the
adhesiveness of the substrate and the adhesive layer; the process
adhesiveness between the electrodes and the separator via the
adhesive layer; and the low-temperature output characteristics of
the secondary battery were measured and evaluated by the following
methods.
[0120] <Glass-Transition Temperature (Tg)>
[0121] The glass-transition temperature (Tg.sub.A) of the
particulate polymer A and the glass-transition temperature
(Tg.sub.B) of the particulate polymer B were measured using a
differential scanning calorimeter (produced by SII Technology,
product name: EXSTAR DSC6220). Specifically, 10 mg of the prepared
particulate polymer was placed in an aluminum pan for each sample.
An empty aluminum pan was used as a reference material. The sample
was placed in the aforementioned differential scanning calorimeter
and measured in a temperature range from -100.degree. C. to
200.degree. C. (heating rate of 10.degree. C./min) to obtain a
differential scanning calorimetry (DSC) curve. The temperature
corresponding to the intersection, in the DSC curve, between the
baseline immediately before an endothermic peak at which a
differential signal (DDSC) reached at least 0.05 mW/min/mg and a
tangent to the inflection point first appearing after the
endothermic peak was calculated as the glass-transition temperature
(.degree. C.). The results are listed in Table 1.
[0122] <Volume-Average Particle Diameter>
[0123] The volume-average particle diameter (D.sub.A) of the
particulate polymer A and the volume-average particle diameter
(D.sub.B) of the particulate polymer B were measured by a laser
diffraction method. Specifically, an aqueous dispersion solution
(adjusted to a solid content concentration of 0.1 mass %) including
the prepared particulate polymer was used as a sample. In a
(volume-based) particle diameter distribution measured using a
laser diffraction particle size analyzer (produced by Beckman
Coulter, Inc., product name: LS-230), the particle diameter D50 at
which the cumulative volume calculated from the small diameter end
reached 50% was taken to be the volume-average particle diameter
(.mu.m). The results are listed in Table 1.
[0124] <Degree of Swelling in Electrolysis Solution>
[0125] The degree of swelling in electrolysis solution of the
particulate polymers was measured by the following method.
Specifically, water dispersions containing the particulate polymers
were placed in a polytetrafluoroethylene petri dish. Each water
dispersion in a petri dish was dried at a temperature of 25.degree.
C. for 48 hours to obtain powdered samples. Approximately 0.2 g of
each sample was pressed for 2 minutes at a temperature of
200.degree. C. and a pressure of 5 MPa to obtain a test specimen.
The measured weight of the resulting test specimen was recorded as
WO.
[0126] Next, the resulting test specimen was immersed in
electrolysis solution at a temperature of 60.degree. C. for 72
hours. A solution containing LiPF.sub.6 at a concentration of 1 M
as a supporting electrolyte in a mixed solvent of ethylene
carbonate (EC), diethyl carbonate (DEC), and vinylene carbonate
(VC) (EC/DEC/VC=68.5/30/1.5 by volume) was used as the electrolysis
solution.
[0127] After immersion, the test specimen was removed from the
electrolysis solution, and the electrolysis solution on the surface
of the test specimen was wiped off. The measured weight of the test
specimen after immersion was recorded as W1.
[0128] Using the measured weights W0 and W1, the degree (factor) of
swelling S in electrolysis solution was calculated as S=W1/W0. The
results are listed in Table 1.
[0129] <Blocking Resistance>
[0130] The blocking resistance of an adhesive layer-equipped
separator for a non-aqueous secondary battery and an adhesive
layer-equipped positive electrode for a non-aqueous secondary
battery was evaluated as follows. Specifically, the produced
adhesive layer-equipped separator for a non-aqueous secondary
battery and adhesive layer-equipped positive electrode for a
non-aqueous secondary battery were each cut into square pieces
measuring 5 cm wide by 5 cm high. Two square pieces were overlapped
so that the adhesive layer surfaces of the adhesive layer-equipped
separators and of the adhesive layer-equipped positive electrodes
faced each other. The overlapped adhesive layer-equipped separators
and the overlapped adhesive layer-equipped positive electrodes were
placed under a pressure of 10 g/cm.sup.2 at 40.degree. C. to obtain
pressed test specimens. The resulting pressed test specimens were
each left standing for 24 hours. For each test specimen that had
been left standing for 24 hours, one square piece of the overlapped
separators or positive electrodes was fixed, the other square piece
was pulled with a force of 0.3 N/m, and the test specimen was
observed to see whether peeling was possible. The adhesion state
(blocking state) was evaluated with the following criteria. Less
observation of the adhesion state indicates better blocking
resistance. The results are listed in Table 1.
[0131] A: The square pieces are not adhered.
[0132] B: The square pieces are adhered but can be peeled
apart.
[0133] C: The square pieces are adhered and cannot be peeled
apart.
[0134] <Adhesiveness Between Substrate and Adhesive
Layer>
[0135] The adhesiveness between the substrate (separator or
positive electrode) and the adhesive layer was measured and
evaluated as the peel strength as follows. Specifically, test
specimens were obtained by cutting each produced adhesive
layer-equipped separator for a non-aqueous secondary battery or
adhesive layer-equipped positive electrode for a non-aqueous
secondary battery into a rectangle measuring 100 mm long by 10 mm
wide. The test specimens were placed with the surface of the
adhesive layer facing down, and cellophane tape (prescribed by JIS
Z1522) was attached to the surface of the adhesive layer. The
cellophane tape had been affixed to a horizontal test stage. The
stress at the time when the substrate (separator or positive
electrode) was peeled by pulling up one end in the vertical
direction at a pulling speed of 50 mm/min was measured. This
measurement was made three times, and the average measured stress
was calculated and taken to be the peel strength (N/m). Using the
measured peel strength, the adhesiveness was evaluated by the
following criteria. A greater peel strength indicates better
adhesiveness between the substrate and the adhesive layer. The
results are listed in Table 1.
[0136] A: Peel strength of at least 70 N/m
[0137] B: Peel strength of at least 40 N/m and less than 70 N/m
[0138] C: Peel strength of less than 40 N/m, or dusting of the
adhesive layer (detachment of adhesive particles)
[0139] <Process Adhesiveness>
Examples 1 to 11 and Comparative Examples 1 to 3
[0140] The process adhesiveness between the electrode (positive
electrode) and the separator via the adhesive layer for a
non-aqueous secondary battery was measured and evaluated as the
peel strength as follows. In this measurement, the positive
electrode serving as the electrode and the separator were placed
opposite each other as an example, but measurements can be made by
the same method when placing the negative electrode and the
separator opposite each other. Specifically, the produced positive
electrode and adhesive layer-equipped separator for a non-aqueous
secondary battery were each cut to measure 50 mm long by 10 mm
wide. The cut positive electrode and adhesive layer-equipped
separator were stacked with the adhesive layer therebetween. The
resulting stacked piece was pressed by a roll press at a process
adhesion temperature (T) of 60.degree. C. and a load of 10 kN/m to
adhere the positive electrode and the separator, thus obtaining a
test specimen.
[0141] The test specimen was placed with the surface of the
positive electrode on the current collector side facing down, and
cellophane tape (prescribed by JIS Z1522) was attached to the
surface of the positive electrode on the current collector side.
The cellophane tape had been affixed on a horizontal test stage.
The stress at the time when the adhesive layer-equipped separator
was peeled by pulling up one end in the vertical direction at a
pulling speed of 50 mm/min was measured. This measurement was made
a total of 3 times. The average measured stress was calculated as
the peel strength (N/m), which was evaluated by the following
criteria as the process adhesiveness between the positive electrode
and the separator via the adhesive layer. A higher peel strength
indicates better process adhesiveness. The results are listed in
Table 1.
Example 12
[0142] The produced adhesive layer-equipped positive electrode for
a non-aqueous secondary battery and the separator were each cut to
measure 50 mm long by 10 mm wide. The cut adhesive layer-equipped
positive electrode for a non-aqueous secondary battery and
separator without an adhesive layer were then stacked with an
adhesive layer therebetween. The resulting stacked piece was
pressed by a roll press at a press adhesion temperature (T) of
60.degree. C. and a load of 10 kN/m to adhere the positive
electrode and the separator, thus obtaining a test specimen.
[0143] The test specimen was placed with the surface of the
positive electrode on the current collector side facing down, and
cellophane tape (prescribed by JIS Z1522) was attached to the
surface of the positive electrode on the current collector side.
The cellophane tape had been affixed on a horizontal test stage.
The stress at the time when the separator was peeled by pulling up
one end in the vertical direction at a pulling speed of 50 mm/min
was then measured. This measurement was made a total of 3 times.
The average measured stress was calculated as the peel strength
(N/m), which was evaluated by the following criteria as the process
adhesiveness between the positive electrode and the separator via
the adhesive layer. A higher peel strength indicates better process
adhesiveness. The results are listed in Table 1.
Example 13
[0144] The resulting stacked piece was pressed by a roll press at a
process adhesion temperature (T) of 30.degree. C. and a load of 10
kN/m to adhere the positive electrode and the separator, thus
obtaining a test specimen.
[0145] Apart from this point, the test specimen was obtained with a
similar method to Example 1, and the process adhesiveness was
evaluated in a similar way to Example 1 with the following
criteria. A higher peel strength indicates better process
adhesiveness. The results are listed in Table 1.
Example 14
[0146] The resulting stacked piece was pressed by a roll press at a
process adhesion temperature (T) of 80.degree. C. and a load of 10
kN/m to adhere the positive electrode and the separator, thus
obtaining a test specimen.
[0147] Apart from this point, the test specimen was obtained with a
similar method to Example 1, and the process adhesiveness was
evaluated in a similar way to Example 1 with the following
criteria. A higher peel strength indicates better process
adhesiveness. The results are listed in Table 1.
[0148] A: Peel strength of at least 30 N/m
[0149] B: Peel strength of at least 15 N/m and less than 30 N/m
[0150] C: Peel strength of at least 0.5 N/m and less than 15
N/m
[0151] D: Peel strength of less than 0.5 N/m
[0152] <Low-Temperature Output Characteristics of Non-Aqueous
Secondary Battery>
[0153] A lithium ion secondary battery as a produced non-aqueous
secondary battery (a 40 mAh stacked laminate cell) was allowed to
stand for 24 hours in a 25.degree. C. environment. The lithium ion
secondary battery was then charged for 5 hours at a charging rate
of 0.1 C in a 25.degree. C. environment, and a voltage measured
after charging was recorded as V0. Next, the lithium ion secondary
battery was discharged at a discharge rate of 1 C in a -10.degree.
C. environment, and a voltage measured 15 seconds after the
initiation of discharge was recorded as V1.
[0154] The voltage change .DELTA.V (defined as V0-V1) was then
calculated, and the low-temperature output characteristics of the
secondary battery were evaluated based on the criteria below. A
smaller value for the voltage change .DELTA.V indicates better
low-temperature output characteristics. The results are listed in
Table 1.
[0155] A: Voltage change .DELTA.V of less than 350 mV
[0156] B: Voltage change .DELTA.V of at least 350 mV and less than
500 mV
[0157] C: Voltage change .DELTA.V of at least 500 mV
Example 1
<Preparation of Particulate Polymer A>
[0158] A reaction vessel equipped with a stirrer was charged with
70 parts of deionized water, 0.15 parts of sodium lauryl sulfate
(produced by Kao Corporation, product name: EMAL 2F) as an
emulsifier, and 0.5 parts of ammonium persulfate as a
polymerization initiator. The gas phase of the reaction vessel was
purged with nitrogen gas, and the contents of the reaction vessel
were heated to 60.degree. C.
[0159] A monomer mixture was prepared in a separate vessel by
mixing 50 parts of deionized water, 0.5 parts of sodium
dodecylbenzenesulfonate as a dispersant, 94 parts of butyl
acrylate, 2 parts of acrylonitrile, 2 parts of methacrylic acid, 1
part of N-methylolacrylamide, and 1 part of allyl glycidyl ether.
The monomer mixture was continuously added to the reaction vessel
over 4 hours to effect polymerization. During addition, the
polymerization reaction was effected while maintaining the
temperature at 60.degree. C. After completion of addition, the
reaction mass was further stirred for 3 hours at 70.degree. C. and
the polymerization reaction was quenched, yielding a water
dispersion of the particulate polymer A, which is an acrylic-based
polymer.
[0160] The glass-transition temperature, volume-average particle
diameter, and degree of swelling in electrolysis solution of the
obtained particulate polymer A were measured. The obtained
particulate polymer A had a glass-transition temperature of
-37.degree. C., a volume-average particle diameter D50 of 380 nm,
and a degree of swelling in electrolysis solution of a factor of
4.0.
[0161] <Preparation of Particulate Polymer B>
[0162] A mixture was obtained by charging a 5 MPa pressure vessel
equipped with a stirrer with 55 parts of methyl methacrylate, 40
parts of butyl acrylate, 4 parts of methacrylic acid, 1 part of
ethylene dimethacrylate, 1 part of sodium dodecylbenzenesulfonate
as an emulsifier, 150 parts of deionized water, and 0.5 parts of
potassium persulfate as a polymerization initiator. After the
mixture was fully stirred, the temperature was raised to 60.degree.
C. to initiate polymerization. When the polymerization conversion
rate reached 98%, the polymerization reaction was quenched by
cooling to produce a water dispersion of the particulate polymer B,
which is an acrylic-based polymer.
[0163] The glass-transition temperature, volume-average particle
diameter, and degree of swelling in electrolysis solution of the
obtained particulate polymer B were measured. The obtained
particulate polymer B had a glass-transition temperature of
47.degree. C., a volume-average particle diameter D50 of 500 nm,
and a degree of swelling in electrolysis solution of a factor of
18.
[0164] <Production of Composition for Adhesive Layer of
Non-Aqueous Secondary Battery>
[0165] In a stirring vessel, 50 parts by mass in terms of solid
content of the particulate polymer A and 100 parts by mass in terms
of solid content of the particulate polymer B obtained as described
above were mixed.
[0166] Then, 1 part by mass of a surface tension modifier (produced
by SAN NOPCO Ltd., product name: SN366) and 1 part of ammonium
polyacrylate (produced by Toagosei Co., Ltd., product name: A6114)
as a dispersant were added to the stirring vessel. Furthermore, the
mixture was diluted with deionized water to obtain a composition
for an adhesive layer of a non-aqueous secondary battery in slurry
form with a 30% solid content concentration.
[0167] <Production of Adhesive Layer-Equipped Separator for
Non-Aqueous Secondary Battery>
[0168] A polypropylene separator (produced by Celgard, LLC.,
product name "Celgard 2500") was prepared. The composition for an
adhesive layer of a non-aqueous secondary battery obtained as
described above was applied to the surface of the prepared
separator using a bar coater and then dried in an oven for 3
minutes at a temperature of 50.degree. C. The same process was
performed on the other surface of the separator to obtain an
adhesive layer-equipped separator for a non-aqueous secondary
battery with an adhesive layer formed on both surfaces (thickness
of each adhesive layer: 1 .mu.m).
[0169] The blocking resistance of the obtained adhesive
layer-equipped separator for a non-aqueous secondary battery and
the adhesiveness between the separator and the adhesive layer were
measured and evaluated by the aforementioned methods. The results
are listed in Table 1.
[0170] <Production of Electrode for Non-Aqueous Secondary
Battery>
<<Negative Electrode>>
[Preparation of Binder]
[0171] A 5 MPa pressure vessel equipped with a stirrer was charged
with 33 parts of 1,3-butadiene, 3.5 parts of itaconic acid, and
63.5 parts of styrene as monomers, 0.4 parts of sodium
dodecylbenzenesulfonate as an emulsifier, 150 parts of deionized
water, and 0.5 parts of potassium persulfate as a polymerization
initiator. The contents of the pressure vessel were sufficiently
stirred and were then heated to 50.degree. C. to initiate
polymerization. The reaction was quenched by cooling at the point
at which the polymerization conversion rate reached 96% to yield a
mixture that contained a particulate binder (styrene-butadiene
copolymer). The mixture was adjusted to pH 8 through addition of a
5% sodium hydroxide aqueous solution, and unreacted monomers were
then removed by thermal-vacuum distillation. Thereafter, the
mixture was cooled to 30.degree. C. or lower to obtain a water
dispersion containing a binder.
[0172] <Preparation of Slurry Composition for Negative
Electrode>
[0173] A mixture containing 100 parts of synthetic graphite
(average particle diameter: 15.6 .mu.m) and 1 part in terms of
solid content of a 2% aqueous solution of sodium salt of
carboxymethyl cellulose (produced by Nippon Paper Industries Co.,
Ltd., product name: MAC350HC) as a thickener was adjusted to a
solid content concentration of 68% with deionized water and was
then mixed for 60 minutes at 25.degree. C. The solid content
concentration was then adjusted to 62% with deionized water, after
which the mixture was further mixed for 15 minutes at 25.degree. C.
to obtain a mixed solution. Next, 1.5 parts in terms of solid
content of the water dispersion containing the above-described
binder and deionized water were added to the obtained mixed
solution, which was adjusted to a final solid content concentration
of 52% and was then further mixed for 10 minutes. The mixed
solution was subjected to a defoaming process under reduced
pressure to yield a highly fluid slurry composition for a negative
electrode.
[0174] [Production of Negative Electrode]
[0175] The slurry composition for a negative electrode obtained as
described above was applied using a comma coater onto one surface
of a copper foil (thickness: 20 .mu.m) as a current collector so
that the dry film thickness would be approximately 150 .mu.m. The
slurry composition was then dried. This drying was performed by
transporting the copper foil with the slurry composition applied
thereon through an oven at 60.degree. C. at a rate of 0.5 m/min
over 2 minutes. Subsequently, the copper foil was heat-treated for
2 minutes at 120.degree. C. to obtain a pre-press web of negative
electrode. The pre-press web of negative electrode was rolled with
a roll press to yield a post-press negative electrode (thickness of
negative electrode mixed material layer: 80 .mu.m).
[0176] <<Positive Electrode>>
[Preparation of Slurry Composition for Positive Electrode]
[0177] A mixture of 100 parts of LiCoO.sub.2 (volume-average
particle diameter: 12 .mu.m) as a positive electrode active
material, 2 parts of acetylene black (produced by Denki Kagaku
Kogyo Kabushiki Kaisha, product name: HS-100) as a conductive
material, and 2 parts in terms of solid content of polyvinylidene
fluoride (produced by Kureha Corporation, product name: #7208) as a
binder was mixed with N-methylpyrrolidone as a solvent to yield a
mixed solution with a total solid content concentration adjusted to
70%. The obtained mixed solution was mixed using a planetary mixer
to yield a slurry composition for a positive electrode.
[0178] [Production of Positive Electrode]
[0179] The slurry composition for a positive electrode obtained as
described above was applied using a comma coater onto one surface
of an aluminum foil (thickness: 20 .mu.m) as a current collector so
that the dry film thickness would be approximately 150 .mu.m. The
slurry composition was then dried. This drying was performed by
transporting the aluminum foil through an oven at 60.degree. C. at
a rate of 0.5 m/min over 2 minutes. Subsequently, the aluminum foil
was heat-treated for 2 minutes at 120.degree. C. to obtain a
pre-press web of positive electrode. The pre-press web of positive
electrode was rolled with a roll press to yield a post-press
positive electrode (thickness of positive electrode mixed material
layer: 80 .mu.m).
[0180] A test specimen was produced as described above using the
obtained positive electrode and the adhesive layer-equipped
separator for a non-aqueous secondary battery, and the process
adhesiveness of the adhesive layer in the test specimen was
measured and evaluated by the aforementioned method. The results
are listed in Table 1.
[0181] <Production of Non-Aqueous Secondary Battery>
[0182] The post-press positive electrode obtained as described
above was cut into a 4 cm.times.4 cm square. The adhesive
layer-equipped separator for a non-aqueous secondary battery
obtained as described above was then cut to 5 cm.times.5 cm and
arranged on the surface of the positive electrode mixed material
layer of the positive electrode. Furthermore, the post-press
negative electrode produced as described above was cut to 4.2
cm.times.4.2 cm and arranged on the surface of the adhesive
layer-equipped separator for a non-aqueous secondary battery not in
contact with the positive electrode mixed material layer, with the
surface of the negative electrode mixed material layer facing the
separator. A laminate was thus obtained. The adhesive
layer-equipped separator for a non-aqueous secondary battery was
formed to have an adhesive layer on both surfaces of the separator.
Next, the obtained laminate was pressed at a temperature of
60.degree. C. and a pressure of 0.5 MPa to obtain a laminate in
which the positive electrode, separator, and negative electrode
were adhered via adhesive layers.
[0183] Subsequently, the adhered laminate was enclosed by an
aluminum packing case as a battery outer package. Electrolysis
solution (solvent: ethylene carbonate (EC)/diethyl carbonate
(DEC)/vinylene carbonate (VC)=68.5/30/1.5 by volume, electrolyte:
LiPF.sub.6 at a concentration of 1 M) was injected so that no air
remained. The opening of the aluminum packing case was then heat
sealed at 150.degree. C., hermetically sealing the aluminum packing
case. Finally, the aluminum packing case portion containing the
adhered laminate was pressed at 60.degree. C. and 0.5 MPa to
produce a lithium ion secondary battery that was a 40 mAh stacked
laminate cell.
[0184] The low-temperature output characteristics of the produced
lithium ion secondary battery were then evaluated. The results are
listed in Table 1.
Example 2
[0185] The particulate polymer A, particulate polymer B,
composition for an adhesive layer of a non-aqueous secondary
battery, adhesive layer-equipped separator for a non-aqueous
secondary battery, electrode for a non-aqueous secondary battery,
and non-aqueous secondary battery were produced in a way similar to
Example 1 except that in the preparation of the particulate polymer
B, the methyl methacrylate was changed to 50 parts and the butyl
acrylate was changed to 45 parts, and the resulting particulate
polymer B had a glass-transition temperature of 35.degree. C., a
degree of swelling in electrolysis solution of a factor of 20, and
a volume-average particle diameter of 450 nm.
[0186] The measurements and evaluations were then performed in the
same manner as for Example 1. The results are listed in Table
1.
Example 3
[0187] The particulate polymer A, particulate polymer B,
composition for an adhesive layer of a non-aqueous secondary
battery, adhesive layer-equipped separator for a non-aqueous
secondary battery, electrode for a non-aqueous secondary battery,
and non-aqueous secondary battery were produced in a way similar to
Example 1 except that in the preparation of the particulate polymer
B, the methyl methacrylate was changed to 58 parts and the butyl
acrylate was changed to 37 parts, and the resulting particulate
polymer B had a glass-transition temperature of 58.degree. C., a
degree of swelling in electrolysis solution of a factor of 17, and
a volume-average particle diameter of 530 nm.
[0188] The measurements and evaluations were then performed in the
same manner as for Example 1. The results are listed in Table
1.
Example 4
[0189] The particulate polymer A, particulate polymer B,
composition for an adhesive layer of a non-aqueous secondary
battery, adhesive layer-equipped separator for a non-aqueous
secondary battery, electrode for a non-aqueous secondary battery,
and non-aqueous secondary battery were produced in a way similar to
Example 1 except that in the preparation of the particulate polymer
A, the butyl acrylate was changed to 74 parts and 20 parts of
2-ethylhexyl acrylate (2-EHA) was added, and the resulting
particulate polymer A had a glass-transition temperature of
-48.degree. C., a degree of swelling in electrolysis solution of a
factor of 3.5, and a volume-average particle diameter of 400
nm.
[0190] The measurements and evaluations were then performed in the
same manner as for Example 1. The results are listed in Table
1.
Example 5
[0191] The particulate polymer A, particulate polymer B,
composition for an adhesive layer of a non-aqueous secondary
battery, adhesive layer-equipped separator for a non-aqueous
secondary battery, electrode for a non-aqueous secondary battery,
and non-aqueous secondary battery were produced in a way similar to
Example 1 except that as the particulate polymer A, the conjugated
diene-based polymer prepared by the following method was used
instead of an acrylic-based polymer.
[0192] The measurements and evaluations were then performed in the
same manner as for Example 1. The results are listed in Table
1.
<Preparation of Particulate Polymer A>
[0193] A 5 MPa pressure vessel equipped with a stirrer was charged
with 42 parts of styrene, 34 parts of 1,3-butadiene, 20 parts of
acrylonitrile, 4 parts of itaconic acid, 0.4 parts of sodium
dodecylbenzenesulfonate as an emulsifier, 150 parts of deionized
water, and 0.5 parts of potassium persulfate as a polymerization
initiator. The contents of the pressure vessel were sufficiently
stirred and were then heated to 50.degree. C. to initiate
polymerization. The reaction was quenched by cooling at the point
at which the polymerization conversion rate reached 96% to yield a
mixture that contained a styrene-butadiene copolymer as the
particulate polymer A. The mixture was adjusted to pH 8 through
addition of a 5% sodium hydroxide aqueous solution, and unreacted
monomers were then removed by thermal-vacuum distillation.
Thereafter, the mixture was cooled to 30.degree. C. or lower to
obtain a water dispersion containing the particulate polymer A.
[0194] The obtained particulate polymer A had a glass-transition
temperature of 13.degree. C., a degree of swelling in electrolysis
solution of a factor of 3.2, and a volume-average particle diameter
of 220 nm.
Example 6
[0195] The particulate polymer A, particulate polymer B,
composition for an adhesive layer of a non-aqueous secondary
battery, adhesive layer-equipped separator for a non-aqueous
secondary battery, electrode for a non-aqueous secondary battery,
and non-aqueous secondary battery were produced in a way similar to
Example 1 except that in the production of the composition for an
adhesive layer of a non-aqueous secondary battery, the amount of
the particulate polymer A was changed to 15 parts in terms of solid
content.
[0196] The measurements and evaluations were then performed in the
same manner as for Example 1. The results are listed in Table
1.
Example 7
[0197] The particulate polymer A, particulate polymer B,
composition for an adhesive layer of a non-aqueous secondary
battery, adhesive layer-equipped separator for a non-aqueous
secondary battery, electrode for a non-aqueous secondary battery,
and non-aqueous secondary battery were produced in a way similar to
Example 1 except that in the production of the composition for an
adhesive layer of a non-aqueous secondary battery, the amount of
the particulate polymer A was changed to 25 parts in terms of solid
content.
[0198] The measurements and evaluations were then performed in the
same manner as for Example 1. The results are listed in Table
1.
Example 8
[0199] The particulate polymer A, particulate polymer B,
composition for an adhesive layer of a non-aqueous secondary
battery, adhesive layer-equipped separator for a non-aqueous
secondary battery, electrode for a non-aqueous secondary battery,
and non-aqueous secondary battery were produced in a way similar to
Example 1 except that in the production of the composition for an
adhesive layer of a non-aqueous secondary battery, the amount of
the particulate polymer A was changed to 65 parts in terms of solid
content.
[0200] The measurements and evaluations were then performed in the
same manner as for Example 1. The results are listed in Table
1.
Example 9
[0201] The particulate polymer A, particulate polymer B,
composition for an adhesive layer of a non-aqueous secondary
battery, adhesive layer-equipped separator for a non-aqueous
secondary battery, electrode for a non-aqueous secondary battery,
and non-aqueous secondary battery were produced in a way similar to
Example 1 except that in the production of the composition for an
adhesive layer of a non-aqueous secondary battery, the amount of
the particulate polymer A was changed to 75 parts in terms of solid
content.
[0202] The measurements and evaluations were then performed in the
same manner as for Example 1. The results are listed in Table
1.
Example 10
[0203] The particulate polymer A, particulate polymer B,
composition for an adhesive layer of a non-aqueous secondary
battery, adhesive layer-equipped separator for a non-aqueous
secondary battery, electrode for a non-aqueous secondary battery,
and non-aqueous secondary battery were produced in a way similar to
Example 1 except that in the preparation of the particulate polymer
B, the methyl methacrylate was changed to 35 parts and 20 parts of
styrene was added, and the resulting particulate polymer B had a
glass-transition temperature of 46.degree. C., a degree of swelling
in electrolysis solution of a factor of 8.0, and a volume-average
particle diameter of 470 nm.
[0204] The measurements and evaluations were then performed in the
same manner as for Example 1. The results are listed in Table
1.
Example 11
[0205] The particulate polymer A, particulate polymer B,
composition for an adhesive layer of a non-aqueous secondary
battery, adhesive layer-equipped separator for a non-aqueous
secondary battery, electrode for a non-aqueous secondary battery,
and non-aqueous secondary battery were produced in a way similar to
Example 5 except that in the preparation of the particulate polymer
A, the styrene was changed to 52 parts, the 1,3-butadiene to 33
parts, and the acrylonitrile to 10 parts, and 1 part of
2-hydroxyethyl-acrylate (.beta.-HEA) was added.
[0206] The obtained particulate polymer A had a glass-transition
temperature of 10.degree. C., a degree of swelling in electrolysis
solution of a factor of 2.0, and a volume-average particle diameter
of 200 nm.
[0207] The measurements and evaluations were then performed in the
same manner as for Example 1. The results are listed in Table
1.
Example 12
[0208] Instead of an adhesive layer-equipped separator for a
non-aqueous secondary battery, a separator without an adhesive
layer was used. Instead of a positive electrode without an adhesive
layer, an adhesive layer-equipped positive electrode for a
non-aqueous secondary battery produced with the following method
was used. The particulate polymer A, particulate polymer B,
composition for an adhesive layer of a non-aqueous secondary
battery, electrode for a non-aqueous secondary battery, adhesive
layer-equipped positive electrode for a non-aqueous secondary
battery, and non-aqueous secondary battery were produced in a way
similar to Example 1 with the further exception that the
non-aqueous secondary battery was produced by the following
method.
[0209] The glass-transition temperature, volume-average particle
diameter, degree of swelling in electrolysis solution, and
low-temperature output characteristics of the secondary battery
were then measured and evaluated in the same manner as for Example
1. The blocking resistance of the adhesive layer-equipped positive
electrode for a non-aqueous secondary battery, the adhesiveness
between the positive electrode and the adhesive layer, and the
process adhesiveness were measured and evaluated in accordance with
the above-described methods. The results are listed in Table 1.
<Production of Adhesive Layer-Equipped Positive Electrode for
Non-Aqueous Secondary Battery>
[0210] A post-press positive electrode obtained as described above
was prepared. The composition for an adhesive layer of a
non-aqueous secondary battery obtained as described above was
applied to the surface of the prepared positive electrode on the
positive electrode mixed material layer side using a bar coater and
then dried in an oven for 3 minutes at a temperature of 50.degree.
C. An adhesive layer-equipped positive electrode for a non-aqueous
secondary battery with an adhesive layer formed on one surface
(single-surface thickness of adhesive layer: 1 .mu.m) was thus
obtained.
<Production of Non-Aqueous Secondary Battery>
[0211] The adhesive layer-equipped positive electrode for a
non-aqueous secondary battery obtained as described above was cut
into a 4 cm.times.4 cm square. A separator not having an adhesive
layer was then cut to 5 cm.times.5 cm and arranged on the surface
of the adhesive layer on the positive electrode mixed material
layer of the positive electrode. Furthermore, the post-press
negative electrode produced as described above was cut to 4.2
cm.times.4.2 cm and arranged on the surface of the adhesive
layer-equipped separator for a non-aqueous secondary battery not in
contact with the positive electrode mixed material layer, with the
surface of the negative electrode mixed material layer facing the
separator. A laminate was thus obtained. Next, the obtained
laminate was pressed at a temperature of 60.degree. C. and a
pressure of 0.5 MPa to obtain a laminate in which the positive
electrode and separator were adhered via an adhesive layer.
[0212] Subsequently, the adhered laminate was enclosed by an
aluminum packing case as a battery outer package. Electrolysis
solution (solvent: ethylene carbonate (EC)/diethyl carbonate
(DEC)/vinylene carbonate (VC)=68.5/30/1.5 by volume, electrolyte:
LiPF.sub.6 at a concentration of 1 M) was injected so that no air
remained. The opening of the aluminum packing case was then heat
sealed at 150.degree. C., hermetically sealing the aluminum packing
case. Finally, the aluminum packing case portion containing the
adhered laminate was pressed at 60.degree. C. and 0.5 MPa to
produce a lithium ion secondary battery that was a 40 mAh stacked
laminate cell.
Example 13
[0213] The particulate polymer A, particulate polymer B,
composition for an adhesive layer of a non-aqueous secondary
battery, adhesive layer-equipped separator for a non-aqueous
secondary battery, electrode for a non-aqueous secondary battery,
and non-aqueous secondary battery were produced in a way similar to
Example 1 except that in the production of the non-aqueous
secondary battery, the obtained laminate was a laminate adhered by
pressing at a temperature of 30.degree. C. and 0.5 MPa.
[0214] The measurements and evaluations were then performed in the
same manner as for Example 1. The results are listed in Table
1.
Example 14
[0215] The particulate polymer A, particulate polymer B,
composition for an adhesive layer of a non-aqueous secondary
battery, adhesive layer-equipped separator for a non-aqueous
secondary battery, electrode for a non-aqueous secondary battery,
and non-aqueous secondary battery were produced in a way similar to
Example 1 except that in the production of the non-aqueous
secondary battery, the obtained laminate was a laminate adhered by
pressing at a temperature of 80.degree. C. and 0.5 MPa.
[0216] The measurements and evaluations were then performed in the
same manner as for Example 1. The results are listed in Table
1.
Comparative Example 1
[0217] The particulate polymer A, particulate polymer B,
composition for an adhesive layer of a non-aqueous secondary
battery, adhesive layer-equipped separator for a non-aqueous
secondary battery, electrode for a non-aqueous secondary battery,
and non-aqueous secondary battery were produced in a way similar to
Example 1 except that in the preparation of the particulate polymer
B, the methyl methacrylate was changed to 95 parts and no butyl
acrylate was used, and the resulting particulate polymer B had a
glass-transition temperature of 100.degree. C., a degree of
swelling in electrolysis solution of a factor of 13, and a
volume-average particle diameter of 530 nm.
[0218] The measurements and evaluations were then performed in the
same manner as for Example 1. The results are listed in Table
1.
Comparative Example 2
[0219] The particulate polymer A, particulate polymer B,
composition for an adhesive layer of a non-aqueous secondary
battery, adhesive layer-equipped separator for a non-aqueous
secondary battery, electrode for a non-aqueous secondary battery,
and non-aqueous secondary battery were produced in a way similar to
Example 1 except that in the preparation of the particulate polymer
B, the methyl methacrylate was changed to 45 parts and the butyl
acrylate was changed to 50 parts, and the resulting particulate
polymer B had a glass-transition temperature of 15.degree. C., a
degree of swelling in electrolysis solution of a factor of 25, and
a volume-average particle diameter of 530 nm.
[0220] The measurements and evaluations were then performed in the
same manner as for Example 1. The results are listed in Table
1.
Comparative Example 3
[0221] The particulate polymer A, particulate polymer B,
composition for an adhesive layer of a non-aqueous secondary
battery, and adhesive layer-equipped separator for a non-aqueous
secondary battery were produced in a way similar to Example 1
except that in the preparation of the particulate polymer A, 67
parts of styrene, 30 parts of 2-ethylhexyl acrylate (2-EHA), and 3
parts of acrylic acid were used instead of the monomers used in
Example 1. Because the adhesive layer in the produced adhesive
layer-equipped separator for a non-aqueous secondary battery
suffered from dusting, neither the electrode for a non-aqueous
secondary battery nor the non-aqueous secondary battery was
produced.
[0222] The obtained particulate polymer A had a glass-transition
temperature of 44.degree. C., a degree of swelling in electrolysis
solution of a factor of 2.0, and a volume-average particle diameter
of 300 nm.
[0223] The glass-transition temperature, volume-average particle
diameter, degree of swelling in electrolysis solution, and
adhesiveness between the separator and adhesive layer were
evaluated in the same manner as for Example 1. The results are
listed in Table 1.
[0224] In Table 1 below, the following abbreviations are used.
"ACL" indicates an acrylic-based polymer. "SBR" indicates a
styrene-butadiene copolymer.
TABLE-US-00001 TABLE 1 Exam- Exam- Exam- Exam- Exam- Exam- Exam-
Exam- Exam- ple 1 ple 2 ple 3 ple 4 ple 5 ple 6 ple 7 ple 8 ple 9
Composition Particulate Type ACL ACL ACL ACL SBR ACL ACL ACL ACL
for adhesive polymer A Content 50 50 50 50 50 15 25 65 75 layer of
(parts by mass) non-aqueous Glass-transition -37 -37 -37 -48 13 -37
-37 -37 -37 secondary temperature Tg.sub.A (.degree. C.) battery
Volume-average particle 380 380 380 400 220 380 380 380 380
diameter D.sub.A (nm) Degree of swelling in 4.0 4.0 4.0 3.5 3.2 4.0
4.0 4.0 4.0 electrolysis solution (factor) Particulate Type ACL ACL
ACL ACL ACL ACL ACL ACL ACL polymer B Content 100 100 100 100 100
100 100 100 100 (parts by mass) Glass-transition 47 35 58 47 47 47
47 47 47 temperature Tg.sub.B (.degree. C.) Volume-average particle
500 450 530 500 500 500 500 500 500 diameter D.sub.B (nm) Diameter
ratio 1.32 1.18 1.39 1.25 2.27 1.32 1.32 1.32 1.32 D.sub.B/D.sub.A
(factor) Degree of swelling in 18 20 17 18 18 18 18 18 18
electrolysis solution (factor) Production conditions Substrate on
which sepa- sepa- sepa- sepa- sepa- sepa- sepa- sepa- sepa-
adhesive layer is formed rator rator rator rator rator rator rator
rator rator Process adhesion 60 60 60 60 60 60 60 60 60 temperature
T (.degree. C.) T - Tg.sub.B (.degree. C.) 13 25 2 13 13 13 13 13
13 Evaluation Blocking resistance A B A B A A A B B categories
Adhesiveness with substrate A A A A B B B A A Process adhesiveness
A A B A B C B A A Low-temperature output characteristics A A A A A
A A B C Compar- Compar- Compar- ative ative ative Exam- Exam- Exam-
Exam- Exam- Exam- Exam- Exam- ple 10 ple 11 ple 12 ple 13 ple 14
ple 1 ple 2 ple 3 Composition Particulate Type ACL SBR ACL ACL ACL
ACL ACL ACL for adhesive polymer A Content 50 50 50 50 50 50 50 50
layer of (parts by mass) non-aqueous Glass-transition -37 10 -37
-37 -37 -37 -37 44 secondary temperature Tg.sub.A (.degree. C.)
battery Volume-average particle 380 200 380 380 380 380 380 300
diameter D.sub.A (nm) Degree of swelling in 4.0 2.0 4.0 4.0 4.0 4.0
4.0 2.0 electrolysis solution (factor) Particulate Type ACL ACL ACL
ACL ACL ACL ACL ACL polymer B Content 100 100 100 100 100 100 100
100 (parts by mass) Glass-transition 46 47 47 47 47 100 15 47
temperature Tg.sub.B (.degree. C.) Volume-average particle 470 500
500 500 500 530 530 500 diameter D.sub.B (nm) Diameter ratio 1.24
2.50 1.32 1.32 1.32 1.39 1.39 1.67 D.sub.B/D.sub.A Degree of
swelling in 8.0 18 18 18 18 13 25 18 electrolysis solution (factor)
Production conditions Substrate on which sepa- sepa- positive sepa-
sepa- sepa- sepa- sepa- adhesive layer is formed rator rator
electrode rator rator rator rator rator Process adhesion 60 60 60
30 80 60 60 -- temperature T (.degree. C.) T - Tg.sub.B (.degree.
C.) 14 13 13 -17 33 -40 45 -- Evaluation Blocking resistance A A A
A A A C * categories Adhesiveness with substrate A B A A A A A C
Process adhesiveness A B B C A D A * Low-temperature output
characteristics B B A A B B C * *particles of adhesive layer
detached, measurement/evaluation impossible
[0225] As is clear from Table 1, particles of the adhesive layer
detached from the separator in Comparative Example 3, which used a
particulate polymer A with a glass-transition temperature exceeding
20.degree. C. Hence, this adhesive layer could not fulfill its
function.
[0226] Furthermore, it is clear that Examples 1 to 14, which used a
particulate polymer A with a glass-transition temperature no higher
than 20.degree. C. and a particulate polymer B with a
glass-transition temperature of at least 30.degree. C. and less
than 60.degree. C., had both better blocking resistance and process
adhesiveness than Comparative Examples 1 and 2, which used a
particulate polymer B with a glass-transition temperature outside
of the aforementioned range.
INDUSTRIAL APPLICABILITY
[0227] The present disclosure can provide an adhesive layer for a
non-aqueous secondary battery that can achieve both high process
adhesiveness and high blocking resistance in battery members such
as an electrode and a separator and can provide a composition for
an adhesive layer of a non-aqueous secondary battery capable of
forming this adhesive layer.
[0228] The present disclosure can also provide an adhesive
layer-equipped separator for a non-aqueous secondary battery, and
an adhesive layer-equipped electrode for a non-aqueous secondary
battery, that have both high process adhesiveness and high blocking
resistance.
[0229] The present disclosure can also provide a non-aqueous
secondary battery with excellent cell characteristics, such as
output characteristics, and a method for producing a non-aqueous
secondary battery that allows production of the non-aqueous
secondary battery while improving the process adhesiveness and
blocking resistance of the battery members.
* * * * *